How high was your chlorine when you tested pH? If it was above 5ppm with that kit, it will cause falsely high pH readings. If that was the case, retest pH before deciding that it needs lowered by diluting the sample as follows. Take 1/4 cup pool water and 1/4 cup distilled water. Use that mix to run the pH test as normal.

If you repeat the test with dilution and still find that the pH is high OR if the chlorine was no higher than 5ppm when you tested the pH originally, then you can lower it with muriatic acid. But, please read the info at this link first:> http://pool9.net/muriatic/

Hope this helps.